Next Article in Journal
The Effect of Calorie Restriction on Protein Quality Control in Yeast
Previous Article in Journal
Plant-Derived Extracellular Vesicles and Their Exciting Potential as the Future of Next-Generation Drug Delivery
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Biomolecules
Volume 13
Issue 5
10.3390/biom13050838
biomolecules-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Research Progress in Calcitonin Gene-Related Peptide and Bone Repair

by
Qichang Wang
1,2,3,4,†,
Haotian Qin
1,2,†,
Jiapeng Deng
1,2,
Huihui Xu
1,2,
Su Liu
1,2,
Jian Weng
1,2,* and
Hui Zeng
1,2,4,*
1
National & Local Joint Engineering Research Center of Orthopaedic Biomaterials, Peking University Shenzhen Hospital, Shenzhen 518036, China
2
Department of Bone & Joint Surgery, Peking University Shenzhen Hospital, Shenzhen 518036, China
3
School of Clinical Medicine, Department of Medicine, Shenzhen University, Shenzhen 518061, China
4
Shenzhen Key Laboratory of Orthopaedic Diseases and Biomaterials Research, Shenzhen 518036, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Biomolecules 2023, 13(5), 838; https://doi.org/10.3390/biom13050838
Submission received: 6 April 2023 / Revised: 8 May 2023 / Accepted: 10 May 2023 / Published: 15 May 2023
Browse Figures
Review Reports Versions Notes

Abstract

:
Calcitonin gene-related peptide (CGRP) has 37 amino acids. Initially, CGRP had vasodilatory and nociceptive effects. As research progressed, evidence revealed that the peripheral nervous system is closely associated with bone metabolism, osteogenesis, and bone remodeling. Thus, CGRP is the bridge between the nervous system and the skeletal muscle system. CGRP can promote osteogenesis, inhibit bone resorption, promote vascular growth, and regulate the immune microenvironment. The G protein-coupled pathway is vital for its effects, while MAPK, Hippo, NF-κB, and other pathways have signal crosstalk, affecting cell proliferation and differentiation. The current review provides a detailed description of the bone repair effects of CGRP, subjected to several therapeutic studies, such as drug injection, gene editing, and novel bone repair materials.

1. Overview of CGRP

1.1. Structure of CGRP

Calcitonin gene-related peptide (CGRP) is a polypeptide with 37 amino acids [1]. There are two main in vivo forms of CGRP, viz., αCGRP and βCGRP. αCGRP is mainly encoded by the calcitonin gene, also called the CALCA gene. It is synthesized post-transcriptionally through specific splicing, synthesizing two αCGRP and CT different products. βCGRP is encoded by the CALCB gene with >90% structural similarity to αCGRP [2]. αCGRP is mainly distributed in central and peripheral nerve fibers. In contrast, βCGRP is primarily distributed in the gastrointestinal tract, possessing similar functions with slightly higher biological efficacy than αCGRP [3]. The current research focuses on αCGRP, and this review is mainly derived from studies on αCGRP. CGRP has four structural domains: 1. The first has the header seven amino acids at the NH2 terminus, with disulfide bonds and a ring structure at residues 2 and 7. They can interact with the transmembrane structural domain of the CLR for receptor activation. The CGRP8-37 antagonist can be generated by removing the first structural domain of CGRP; 2. the second structural domain has 8–18 residues, and their absence causes a 50- to 100-fold decrease in CGRP affinity; 3. the third structural domain includes 19–27 residues, forming a hinge region; 4. the fourth structural domain possesses the remaining 28–37 residues at the COOH end, serving as two receptor-binding epitopes [1,4]. The two structural domains at the NH2 and COOH ends are the most important in the receptor binding process. The COOH end binds to the extracellular structural domain (ECD) of the receptor. In contrast, the disulfide ring at the same NH2 end attaches to the transmembrane structural domain (TM) and the extracellular loop (ECL) region. This activates the receptor and transmits signals to the intracellular compartment [5].

1.2. Receptors of CGRP

Currently, receptors and related regulatory proteins of CGRP mainly include calcitonin gene-related peptide receptor (CLR) and receptor activity modifying protein 1 (RAMP1). CLR is a seven-transmembrane receptor protein responding to adrenocorticotropin-releasing factor (CRF) and frog skin peptide [6]. However, cell lines constructed using CLR alone had no significant correlation with CGRP stimulation [7]. RAMP1 exists in mammalian cells, which, when co-expressed with CLR, CGRP can bind to CLR to exert biological effects [8]. Follow-up studies revealed that RAMP1 transports CLR to the cell membrane surface. This creates a CLR-RAMP1 dimer for CGRP to bind and function with CLR; thus, RAMP1 is essential for CLR function [9].
In addition, a new CGRP receptor-related protein, receptor component protein (RCP), enhances the CGRP effects [10]. RCP regulates CGRP/CLR-RAMP1 cell signaling [11], and immunoprecipitation indicates mutual binding sites between CLR and RCP. It is unclear whether RCP is necessary for CLR activation by CGRP. Therefore, further experiments must explore the specific function of RCP [12].

1.3. CGRP Synthesis, Storage, and Release

CGRP is mainly synthesized in sensory nerve fibers [13], stored, and released as vesicles [14]. The most representative cells are the spinal dorsal root ganglion (DRG) and the trigeminal ganglion. They are the primary sensory neurons and one of the most abundant CGRP sites. Membrane potential alterations lead to the spinal DRG triggering Ca2+ influx and activating the Ca2+/CaMKII/CREB signaling cascade, synthesizing CGRP. Then, CGRP is transported to peripheral nerve endings and released after membrane depolarization [15]. The trigeminal ganglion is also rich in CGRP; its CGRP-positive neurons account for half [16]. Other sites, such as autonomic ganglia and cerebral vessels, are also rich in CGRP [17,18,19]. The CGRP receptors have a wide range and various biological effects due to wide distribution.

1.4. Physiology and Pathophysiology of CGRP

Research has confirmed that the secretion of CGRP has a circadian rhythm in vivo, with a higher amount released into plasma at night [20]. The half-life of CGRP secreted by the body is relatively short, typically less than 10 min. This short half-life is due to the rapid metabolism and clearance of the peptide by various enzymes and organs in the body, such as the liver and kidneys [21]. Under physiological conditions, CGRP primarily exerts its effects locally, particularly in the peripheral nervous and vascular systems, where it mainly mediates vasodilation and pain transmission.
CGRP is a diastolic microvascular agent and mediates vasodilation [22]. CGRP is 10-fold more potent than prostaglandins and 10–100-fold more potent than neuropeptide vasodilators, including ACh and SP. CGRP has selective modulatory effects on cerebral, coronary, and renal vasculature. Moreover, the vasodilatory effect of CGRP is longer lasting than other vasodilators. However, CGRP does not regulate systemic blood pressure in normal individuals [23,24]. It was believed that the powerful vasodilatory effects of CGRP could develop novel antihypertensive drugs. However, in vivo experiments did not correlate CGRP with systemic blood pressure regulation.
CGRP mediates nociceptive transmission CGRP [25], as they act as afferent neurotransmitters after being released by sensory neurons to conduct nociception [26]. CGRP release is associated with somatic, visceral, neuropathic, and inflammatory pain [27]. Research has found that the pain-mediating ability of CGRP is weaker than that of substance P [28]. It is important to note that the efficacy of CGRP observed in different animal models can vary [29]. The role of CGRP in pain has been controversial, with some studies suggesting that it can induce hyperalgesia, or increased sensitivity to painful stimuli [1]. However, there is already much evidence regarding the association between CGRP and migraine [30,31,32]. CGRP is extremely high in the trigeminal ganglion and is selectively released from the trigeminal nervous system during acute migraine. CGRP receptor antagonists and monoclonal antibodies effectively relieve migraine [33]. The pain-relieving effect of CGRP monoclonal antibodies is substantial in treating chronic inflammatory conditions (osteoarthritis, chronic low back pain, migraine or rheumatoid arthritis, etc.) [34]. Developing novel analgesic agents targeting CGRP antagonism is of considerable scientific interest. Table 1 summarizes the most representative CGRP antagonists.
Under pathological conditions, due to the widespread expression of CGRP receptors throughout the body, abnormal CGRP secretion may impact various physiological systems, including the circulatory system, nervous system, skeletal muscle system, and endocrine system. Abnormal CGRP secretion has been associated with an increased risk of neuralgia, ischemic heart disease, atherosclerosis, chronic joint inflammation, obesity, diabetes, and other diseases [1,22,47,48]. Therefore, understanding the role of CGRP in these physiological processes is important for developing effective treatments for these diseases.

2. Effects of CGRP on Bone Repair

CGRP is widely distributed in bone tissue and promotes osteogenesis, inhibits osteolysis, induces angiogenesis, and regulates the immune microenvironment (Figure 1).

2.1. Distribution of CGRP and Receptors in Bone Tissue

Bone tissue is rich in CGRP, with two types of nerve fibers—substance P (SP)-positive and CGRP-positive nerve fibers. They are mainly present in bone, bone marrow, periosteum, synovium, and adjacent soft tissues. The proportion of CGRP-positive nerve fibers is dominant [49], and CGRP is a critical node that cannot be bypassed and is a bridge between nerve and bone repair. The receptors of CGRP, CLR, and RAMP1 are widely distributed in vivo, and the co-localized expression of CLR and RAMP1 is also crucial for CGRP to exert its effects. In bone tissue, macrophages, osteoblasts, and vascular tissue, CLR and RAMP1 expression is abundant in macrophages, osteoblasts, and endothelial cells [50,51,52,53,54]. This regulates osteogenesis by affecting the immune microenvironment, vasculature, and accompanying nerves. Immune cells promote bone production by secreting certain osteogenic factors [55]. In contrast, blood vessels and nerve fibers are distributed throughout the bone tissue, providing oxygen, nutrients, and supporting cells to the bone tissue. Therefore, they are essential in bone growth, development, and fracture healing [56]. In short, sensory neurons are stimulated to continuously release CGRP into bone tissue to achieve neurological bone regulation.

2.2. CGRP Promotes Osteogenesis

Among the neuropeptides identified in bone tissue (CGRP, SP, NE, NPY), CGRP is most strongly associated with bone repair [57]. Mice with a systemic knockout of the CGRP gene have significantly reduced bone mass. In contrast, overexpression of the CGRP gene significantly enhances bone density [58,59]. Therefore, CGRP promotes bone repair accompanied by nerve fiber ingrowth. There were fewer CGRP-positive nerve fibers at inflammatory progression sites (larger defect sites) and more CGRP-positive nerve fibers at repair sites (smaller defects) during knee and ankle osteoarthritis. Thus, inflammation destroying bone may induce the ingrowth of CGRP-positive fibers, producing CGRP for local bone repair [60]. Sequencing results indicate that CGRP promotes extracellular matrix production, which may be an essential pathway for its bone repair effects [54]. Sensory nerves maintain extracellular matrix (ECM) homeostasis through the CGRP/CHSY1 axis, and the knockdown of sensory nerve CGRP induces similar disturbances in ECM metabolism [61].
CGRP can upregulate various osteogenic factors and promote osteoblast anabolism [62,63]. Haitao et al. observed that CGRP promotes elevated levels of cAMP, ATF4, and OCN expression in osteoblasts [64]. ATF4 is an ATF/CREB family member, a cell-specific CREB-related transcriptional essential for osteoblast differentiation and function factor [65]. ATF4 is identified as an osteoblast-specific transcription factor necessary for OCN transcription, an osteoblast-specific marker commonly used to indicate late osteoblast differentiation [66,67]. BMP2 is essential in osteogenesis induction and promotes ECM expression, mainly collagen production and calcium salt formation, using the Smad pathway [68,69,70]. In MG-63 cells, BMP2 can be involved in CGRP-induced osteogenic differentiation, and cAMP/p-CREB upregulation further promotes BMP2 expression [71]. Dental pulp stem cells (DPSCs) possess the qualities of bone marrow mesenchymal stem cells and are the primary source of dentin mineralization. CGRP directly stimulates a 1.8-fold increase in BMP2 mRNA expression in DPSCs, and a 2.8-fold increase in basal levels of cAMP, which promotes dentin formation. Liping et al. observed that CGRP stimulated bone marrow MSC proliferation, upregulated osteoblast gene expression, enhanced alkaline phosphatase activity, and increased calcium nodules in bone marrow mesenchymal stem cells (BMSCs) [72]. Direct action of CGRP on BMSCs elevated the migratory capacity and osteogenic differentiation and inhibited the bone marrow differentiation of MSCs to adipocytes [54,73]. This process involves molecular crosstalk between Wnt/β-catenin and CGRP signaling [74] other than enhanced cAMP response element binding protein 1 in periosteal-derived stem cells (CREB1) and SP7 (osterix, OSX) expression in periosteal-derived stem cells. Thus, osteogenic differentiation of periosteal-derived stem cells is promoted [75]. In vivo studies identified elevated CGRP levels in mice with femoral fractures [76]. Similar upregulatory effects could be seen when serum CGRP expression was examined in femoral neck fracture patients [77]. CGRP was used to transiently act on bone healing tissue and bone formation regulators (IL1b, Ccl7, MMP13, Mrc1), which increased the PPARγ pathway (Adipoq, Fabp4, Scd1, Cfd) members [76]. Thus, local bone defect repairing was induced by releasing CGRP from nerve endings within the periosteum [75]. Electrical stimulation (ES) of the spinal dorsal root ganglion directly enhances the biosynthesis and release of CGRP by activating Ca2+ and accelerating femur fracture healing in osteoporotic rats [15]. Therefore, CGRP is essential in the early generation of bone healing tissue by activating osteogenic effect-related pathways. CGRP also promotes the production of osteogenic factors, collagen, and extracellular matrix, facilitating bone repair.

2.3. CGRP Inhibits Bone Resorption

CGRP inhibits osteoclasts, increases bone volume, and reduces bone resorption [58,78]. Previous studies have indicated that sympathetic and sensory nerves are cross-linked to the osteoclastic effect. In contrast, CGRP reverses the isoproterenol (Isp)-mediated osteoclastic effect [79] and inhibits the proliferation of granulocyte-macrophage lineage progenitor cells (precursor osteoclast cells) [80]. CGRP increases OCN and OPG in osteoblasts and inhibits RANKL expression [64]. RANKL is a RANK ligand, an activatable NF-κB pathway that promotes the proliferation and effects of osteoclasts. CGRP inhibits osteogenesis by suppressing RANKL expression, inhibiting the NF-κB pathway, and downregulating the expression of osteoclast TRAP and histone K [72]. However, NF-κB also has a vital role in senescence and apoptosis, and attention must be paid to whether CGRP plays a crucial role in their senescence and apoptosis.

2.4. CGRP-Induced Angiogenesis

CGRP is vital in blood vessel formation and growth [81] and can indirectly affect bone development and formation [82,83]. Bone development cannot be separated from the expression of CGRP, vascular endothelial growth factor (VEGF), a cluster of differentiation 31 (CD31), and lymphatic vessel endothelial hyaluronan receptor 1 (LYVE1) [84]. CGRP-positive nerve fibers during early embryonic development are present in blood vessels, developing muscles, or developing cartilage bones [85]. Angiogenesis and bone regeneration were observed by local CGRP injection into the defect site in rats [86]. CGRP promotes VEGF expression to enhance endothelial cell proliferation and migration [87,88], a mechanism validated in tumor-associated angiogenesis [89]. Moreover, CGRP promotes endothelial progenitor cell proliferation and restricts apoptosis by inhibiting MAPK signaling [90]. OCN upregulation, ALP gene expression, and increase in mineralized nodules in osteoblast (OB) monoculture and human umbilical vein endothelial cell (HUVEC) OB co-culture systems could be associated with particular cytokine expression regulation in HUVEC by CGRP [91]. Biodegradable biomagnesium implants can accelerate bone repair by upregulating CGRP and promoting angiogenesis [92]. BMSCs overexpressing CGRP can improve bone repair by promoting peripheral angiogenesis in diabetic rats having tibial defects [93]. CGRP release at the bone defect site can contribute to angiogenesis, enhancing repair [94].

2.5. CGRP Regulates the Immune Microenvironment

Inflammation occurrence is essential for bone repair [95,96]. Mice with CGRP knockdown exhibit a higher degree of oxidative stress accompanied by reduced nitric oxide synthase (NOS) expression, increased phosphorylated p47 expression, elevated 4 hydroxynonenal (4HNE) levels, and macrophage infiltration [97]. CGRP inhibits LPS-induced TNFα production by macrophages [98] and osteoblasts [99]. Sensory nerve fibers secrete CGRP to inhibit inflammation by suppressing type 1 T helper cytokine production and leukocyte proliferation. CGRP affects the polarization of M0-type to M2-type macrophages, affecting bone tissue remodeling in the later stages of fracture repair [100]. Moreover, CGRP induces bone regeneration and differentiation by elevating M2-type macrophage proportion [101]. Lack of CGRP promotes M1 and inhibits M2 polarization in macrophages. Thus, CGRP knockdown mice hinder osseointegration in bone grafts, and its overexpression improves osseointegration by regulating the macrophage phenotype [102].
However, osteogenic factors (BMP2, BMP6, WNT10b, and OSM) secreted by M2 macrophages were reduced in the early stages and elevated at later stages of CGRP action [103]. Pajarinen et al. indicated that proper inflammation is beneficial in the early stages of bone repair. M1 macrophages may exert their effects in the early and middle stages of osteogenesis. In contrast, M2 macrophages later affect bone matrix mineralization [55], which aligns with the prevailing view of immune regulation of bone repair. Thus, CGRP plays a vital role in regulating the immune microenvironment for bone repair [96,104].
To summarize, CGRP promotes osteogenesis by regulating diversified cells. Table 2 shows a study on CGRP at the cellular level.

3. Effect of CGRP on Osteogenic Effect Pathways

3.1. Major Pathways of CGRP—G Protein-Coupled Receptor Pathway

The CGRP effector pathway was mainly the G protein-coupled receptor pathway (Figure 2).
When CGRP acts on pancreatic cells, the intracellular cAMP concentration increases persistently [114]. Similar phenomena were observed when CGRP acted on vascular endothelial cells and osteoblasts [107,115]. Subsequent studies observed that Gs protein (Stimulatory G protein) has a high-affinity binding site to CGRP [108,110,116]. Main et al. pointed out that CLR is a G protein-coupled receptor that transmits biological signals downstream by increasing the intracellular cAMP concentration [117].
CLRs belong to the class B “secretin” family of G protein-coupled receptors (GPCRs) [1] with significant biological effects of CGRP. Two major classical GPCR signaling pathways are 1. Gαs-CLR/cAMP/PKA pathway: CLR first binds to RAMP1, transports CLR to the cell surface, and couples with Gαs-type G proteins to activate the cell surface enzyme adenylate cyclase. This converts adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP), followed by protein kinase A (PKA) activation. PKA continues to activate cyclic AMP effector element binding protein (CREB) into the nucleus to produce active phosphorylated cyclic AMP effector element binding protein (p-CREB). This promotes transcription of osteogenic-related factors, including BMP2, RUNX2, and SP7, and exerts osteoinductive effects; 2. Gαq/11-CLR/IP3/Ca2+ and Gαq/11-CLR/DAG/PKC pathways: the increased phospholipase C β1 (PLCβ1) activity of Gαq/11 cleaves phosphatidylinositol-4,5-bisphosphate (PIP2) to inositol-1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 acts on the IP3 receptor on the endoplasmic reticulum membrane, leading to Ca2+ efflux into the cytoplasm. Moreover, diacylglycerol promotes protein kinase C (PKC) activity [118,119] and downward activation of osteogenic protein expression. However, intracellular cAMP concentration was much higher than Ca2+ after CGRP treatment. Therefore, CGRP may favor the Gαs-CLR/cAMP/PKA pathway with a downward signal for biological effects [120].

3.2. Other Signal Pathway Crosstalk

The non-G protein-coupled pathway for the osteogenic effect of CGRP is less studied. The classical Wnt signaling pathway is an important regulator involved in bone metabolism [121]. CGRP can inhibit the apoptosis of osteoblasts by regulating the classical Wnt signaling pathway [109]. Moreover, CGRP participation can activate the Wnt pathway to promote BMSCs to osteoblast lineage differentiation [74]. The osteogenic differentiation ability of BMSCs is modulated by affecting the Hippo/Yap pathway [106]. CGRP also affects the Hippo/Yap pathway to control the osteogenic-inducing factor secretion by M2-type macrophages [103]. CGRP promotes BMSC differentiation toward endothelial cells and promotes vascular ingrowth using the PI3K-AKT pathway [86]. CGRP reduces RANKL, increases OPG levels, and inhibits bone resorption by inhibiting the NF-κB pathway [111]. However, the above pathways are not directly activated by CGRP, which possesses specific binding receptor CLR, and receptor-regulated protein RAMP1. Therefore, activating the above pathways is more likely to signal crosstalk generated by activating G protein-coupled pathways. More future studies are needed to determine the effects of CGRP pathway activation.

4. CGRP in Orthopedic Treatment

4.1. Prospects for the Application of CGRP as a Drug

Scientists accelerate the clinical conversion of CGRP by performing animal experiments. Table 3 shows a study on CGRP at the animal level. Scientists consider that CGRP has good application prospects as a drug.
CGRP drug has not been used in clinical practice despite having anti-osteoporotic and osteoinductive effects [63]. Regular intravenous supplementation of CGRP in aged osteoporotic mice significantly increased osteogenesis and decreased bone marrow fat accumulation [54,105]. CGRP carriage as a drug into calcium phosphate bone cement (Sr-CPC) significantly enhanced cell proliferation and elevated ALP secretion in BMSCs [124]. Adipose mesenchymal stem cells (ADSCs) overexpressing CGRP promote the expression of collagen type I (COL1) and bone bridging protein (OPN) with a stronger potential to differentiate into osteoblasts in vitro. Moreover, transplantation of ADSCs overexpressing CGRP into bone defect sites can cause osteopathic effects [113]. BMSCs overexpressing CGRP also possessed better osteogenic effects. Thus, BMSCs carried into collagen scaffolds were more capable of repairing cranial defects in rats [125]. However, direct CGRP trigger supplementation enhances local pain, suggesting a debatable medicinal value of CGRP.

4.2. Biomaterials Can Promote Bone Repair by Modulating CGRP

Although the CGRP drug has not been intensively studied, promoting CGRP expression in vivo for osteogenesis is a potent research topic. Previous studies demonstrated that CGRP has a vital role in bone repair. CGRP-positive nerve fibers are widely distributed in the periosteum and bone marrow [126]. Promoting CGRP release and elevating its local concentration is a more reliable fracture treatment to accelerate bone healing. CGRP is mainly found in vesicles in vivo. Researchers have extracted extracellular vesicles (EV) from adipose mesenchymal stem cells and carried CGRP-rich EV in polylactic acid-hydroxyacetic acid copolymer (PLGA) to enhance the growth of alveolar bone and improve bone repair [128]. Magnesium (Mg) could promote CGRP release and accelerate the bone repair process [75,94]. Mg and its alloys have good biodegradability and biocompatibility and can become bone-replacement materials [129]. Larger healing bone tissues with significantly increased mechanical strength were observed when Mg rods were implanted at the fracture site in osteoporotic rats. Mg promotes osteogenic effects by releasing CGRP from the dorsal root ganglion (DRG) and periosteal nerve fibers and activating cAMP/CREB signaling, wherein periosteal-derived stem cells were identified as CGRP targets [75]. A follow-up study observed that implanting Mg nails into the bone defect site and distraction osteogenesis elevated CGRP concentration in the new bone tissue. Furthermore, this accelerated vascular growth into the bone defect site and bone repair through the CGRP/FAK/VEGF signaling axis [94].

4.3. Modulation of CGRP for Bone Repair by Electrical Stimulation

Electrical stimulation promotes the long entry of CGRP-positive nerve fibers inside the damaged area [130]. Researchers have promoted the biosynthesis and release of CGRP directly during discharge by placing electrodes in the dorsal root ganglion area of the lumbar spine. This enhances osteoporotic fracture healing within the rat femur [15].

5. Other Insights on CGRP and Bone Repair Studies

Therefore, CGRP is an essential link in bone repair, but various voices have emerged. Hoff et al. observed that the offspring of mice knocked out the CALCA gene (equivalent to knocking out both CT and CGRP) had no individual developmental defects. However, there was an increase in bone mass, with a significant increase in bone trabeculae volume and a 1.5- to 2-fold enhancement in bone formation at 1 and 3 months of age [122]. Wear particles produced by joint prostheses induce bone resorption. CALCA gene-deficient wear particle-stimulated aged mice indicated a significant increase in OPG and OCN and a significant decrease in RANKL compared to wild-type mice. Thus, CGRP downregulation in aged mice could enhance osteoprotective effects [123].
BMPs may increase sensory neurogenic CGRP expression [131], and BMP2 is essential for bone formation. However, the relationship between BMP2 and CGRP is quite specific, with substance P synergizing with BMP2 to elevate the osteogenic differentiation of MC3T3-E1 and C2C12. In contrast, the concomitant addition of CGRP reverses the osteoinductive effect, significantly inhibiting osteogenesis [132]. Although the osteoinductive effect of CGRP is well-established, the mechanistic studies are underdeveloped due to harsh in vitro culture conditions of neuronal cells. Moreover, the progress of the in vitro studies lags behind the in vivo studies, and the osteoinductive effect of CGRP could result from the characteristic conditions. These findings are inconsistent with previous studies, which should be addressed in future studies.

6. Conclusions and Perspectives

CGRP is an important neuropeptide, and previous studies have found that it has important effects such as vasodilation and pain conduction. With the deepening of research, the important role of CGRP in promoting bone repair has also been revealed [133]. All tissues and organs of the body do not work independently. The nervous system promotes bone repair by secreting CGRP and acting on osteoblasts, osteoclast, vascular endothelial cells, and macrophages. CGRP may be an important bridge connecting the nervous system, circulatory system, immune system, and skeletal muscle system. In vitro studies found that CGRP exerts its biological effect by activating the CLR-RAMP1 dimer on the cell surface. CLR belongs to the G protein-coupled receptor, and RAMP1 is the regulatory protein of CLR. Together, CGRP can promote CREB entering the nucleus and phosphorylation activation, enhance mRNA transcription, and promote the expression of osteogenic factors such as BMP2 and SP7 to promote bone formation by increasing the concentration of intracellular cAMP. In vivo studies have found that CGRP can promote bone formation, promote vascular growth, inhibit osteoclasis, and regulate the immune microenvironment to promote bone repair. When the body is injured, the CGRP at the fracture site can quickly reach the peak, promote the formation of a larger callus locally, and directly enhance the expression of osteogenic factors such as BMP2 and SP7. As time goes on, the CGRP effect gradually decreases, and bone formation slows down. At this time, the activity of osteoclast increases, and then the ability of bone remodeling increases. In terms of immune regulation, early pro-inflammatory responses are crucial for bone repair. CGRP can inhibit the function of M2 macrophages in the early stage and promote the expression of M2 macrophages and osteogenic-related factors in the later stage. In addition, CGRP can also promote the generation of vascular lymphatic vessels and promote the occurrence of distraction osteogenesis.
Developing peptide drugs that promote bone formation and inhibit osteoporosis based on CGRP has good prospects. Peptides as therapeutic agents have advantages such as high efficiency, high selectivity, and low toxicity. However, many peptides have disadvantages such as poor oral bioavailability, strong hydrophobicity, and fast metabolism in vivo [134]. Natural peptides are usually not suitable for direct clinical use as therapeutic agents. Overcoming the shortcomings of natural peptides through reasonable design is the future direction of peptide therapy [135]. Previous studies have found that CGRP is closely related to various types of pain, and CGRP receptors are widely expressed. If CGRP drugs are used throughout the body, there may be many side effects. Currently, there are no literature reports on the application of CGRP drugs in bone repair, and avoiding CGRP-mediated pain and vascular relaxation to highlight their bone repair effect is a difficulty in related research. More clever structural design of CGRP drugs can serve as an important breakthrough direction. Although CGRP has been limited in drug development, local drug delivery systems and in vivo CGRP activation can still serve as the development direction of CGRP therapy, including stent-carrying CGRP, electrical stimulation of nerve cell secretion of CGRP, and magnesium ions promoting CGRP secretion and subsequently bone repair, which have been validated [15,75,94,128]. CGRP promoting bone repair is the focus of future research. Our team has currently conducted research on magnesium ion regulation of CGRP promoting bone repair, and on the enhancement of osteogenic effect by overexpressing CGRP in BMSCs. This may provide new ideas for the clinical transformation of materials science and stem cell therapy, and also open up a new path for the therapeutic efficacy of bone repair. Therefore, CGRP is an essential link in communicating nerve-bone repair, with promising applications in bone repair.

Author Contributions

Conceptualization, J.W. and H.Z.; writing-original draft preparation, Q.W. and H.Q.; writing-review and editing, H.X. and S.L.; illustration-making, J.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research was continuously funded by National Natural Science Foundation of China (No. 82172432; 82001319 and 82102568), National & Local Joint Engineering Research Center of Orthopaedic Biomaterials (XMHT20190204007), Shenzhen Key Laboratory of Orthopedic Diseases and Biomaterials Research (ZDSYS20220606100602005), Shenzhen Key Medical Discipline Construction Fund (No. SZXK023), Shenzhen “San-Ming” Project of Medicine (No. SZSM201612092), Research and Development Projects of Shenzhen (No. Z2021N054), and Shenzhen Science and Technology Program (No. JCYJ20210324110214040 and JCYJ20190809152409606).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Russell, F.A.; King, R.; Smillie, S.J.; Kodji, X.; Brain, S.D. Calcitonin gene-related peptide: Physiology and pathophysiology. Physiol. Rev. 2014, 94, 1099–1142. [Google Scholar] [CrossRef]
  2. Edvinsson, L. The Trigeminovascular Pathway: Role of CGRP and CGRP Receptors in Migraine. Headache 2017, 57, 47–55. [Google Scholar] [CrossRef] [PubMed]
  3. Mulderry, P.K.; Ghatei, M.A.; Spokes, R.A.; Jones, P.M.; Pierson, A.M.; Hamid, Q.A.; Kanse, S.; Amara, S.G.; Burrin, J.M.; Legon, S.; et al. Differential expression of alpha-CGRP and beta-CGRP by primary sensory neurons and enteric autonomic neurons of the rat. Neuroscience 1988, 25, 195–205. [Google Scholar] [CrossRef] [PubMed]
  4. Conner, A.C.; Hay, D.L.; Howitt, S.G.; Kilk, K.; Langel, U.; Wheatley, M.; Smith, D.M.; Poyner, D.R. Interaction of calcitonin-gene-related peptide with its receptors. Biochem. Soc. Trans. 2002, 30, 451–455. [Google Scholar] [CrossRef] [PubMed]
  5. Watkins, H.A.; Rathbone, D.L.; Barwell, J.; Hay, D.L.; Poyner, D.R. Structure-activity relationships for α-calcitonin gene-related peptide. Br. J. Pharmacol. 2013, 170, 1308–1322. [Google Scholar] [CrossRef]
  6. Chang, C.P.; Pearse, R.V., 2nd; O’Connell, S.; Rosenfeld, M.G. Identification of a seven transmembrane helix receptor for corticotropin-releasing factor and sauvagine in mammalian brain. Neuron 1993, 11, 1187–1195. [Google Scholar] [CrossRef]
  7. Flühmann, B.; Muff, R.; Hunziker, W.; Fischer, J.A.; Born, W. A human orphan calcitonin receptor-like structure. Biochem. Biophys. Res. Commun. 1995, 206, 341–347. [Google Scholar] [CrossRef]
  8. Aiyar, N.; Rand, K.; Elshourbagy, N.A.; Zeng, Z.; Adamou, J.E.; Bergsma, D.J.; Li, Y. A cDNA encoding the calcitonin gene-related peptide type 1 receptor. J. Biol. Chem. 1996, 271, 11325–11329. [Google Scholar] [CrossRef] [PubMed]
  9. McLatchie, L.M.; Fraser, N.J.; Main, M.J.; Wise, A.; Brown, J.; Thompson, N.; Solari, R.; Lee, M.G.; Foord, S.M. RAMPs regulate the transport and ligand specificity of the calcitonin-receptor-like receptor. Nature 1998, 393, 333–339. [Google Scholar] [CrossRef]
  10. Luebke, A.E.; Dahl, G.P.; Roos, B.A.; Dickerson, I.M. Identification of a protein that confers calcitonin gene-related peptide responsiveness to oocytes by using a cystic fibrosis transmembrane conductance regulator assay. Proc. Natl. Acad. Sci. USA 1996, 93, 3455–3460. [Google Scholar] [CrossRef]
  11. Egea, S.C.; Dickerson, I.M. Direct interactions between calcitonin-like receptor (CLR) and CGRP-receptor component protein (RCP) regulate CGRP receptor signaling. Endocrinology 2012, 153, 1850–1860. [Google Scholar] [CrossRef] [PubMed]
  12. Evans, B.N.; Rosenblatt, M.I.; Mnayer, L.O.; Oliver, K.R.; Dickerson, I.M. CGRP-RCP, a novel protein required for signal transduction at calcitonin gene-related peptide and adrenomedullin receptors. J. Biol. Chem. 2000, 275, 31438–31443. [Google Scholar] [CrossRef]
  13. Choi, J.E.; Di Nardo, A. Skin neurogenic inflammation. Semin. Immunopathol. 2018, 40, 249–259. [Google Scholar] [CrossRef]
  14. Arkless, K.; Argunhan, F.; Brain, S.D. CGRP Discovery and Timeline. Handb. Exp. Pharmacol. 2019, 255, 1–12. [Google Scholar] [PubMed]
  15. Mi, J.; Xu, J.K.; Yao, Z.; Yao, H.; Li, Y.; He, X.; Dai, B.Y.; Zou, L.; Tong, W.X.; Zhang, X.T.; et al. Implantable Electrical Stimulation at Dorsal Root Ganglions Accelerates Osteoporotic Fracture Healing via Calcitonin Gene-Related Peptide. Adv. Sci. (Weinh) 2022, 9, e2103005. [Google Scholar] [CrossRef]
  16. Messlinger, K. The big CGRP flood-sources, sinks and signalling sites in the trigeminovascular system. J. Headache Pain 2018, 19, 22. [Google Scholar] [CrossRef]
  17. McCulloch, J.; Uddman, R.; Kingman, T.A.; Edvinsson, L. Calcitonin gene-related peptide: Functional role in cerebrovascular regulation. Proc. Natl. Acad. Sci. USA 1986, 83, 5731–5735. [Google Scholar] [CrossRef]
  18. Ursell, P.C.; Ren, C.L.; Albala, A.; Danilo, P., Jr. Nonadrenergic noncholinergic innervation. Anatomic distribution of calcitonin gene-related peptide-immunoreactive tissue in the dog heart. Circ. Res. 1991, 68, 131–140. [Google Scholar] [CrossRef] [PubMed]
  19. Gupta, S.; Amrutkar, D.V.; Mataji, A.; Salmasi, H.; Hay-Schmidt, A.; Sheykhzade, M.; Messlinger, K.; Olesen, J.; Jansen-Olesen, I. Evidence for CGRP re-uptake in rat dura mater encephali. Br. J. Pharmacol. 2010, 161, 1885–1898. [Google Scholar] [CrossRef]
  20. Portaluppi, F.; Trasforini, G.; Margutti, A.; Vergnani, L.; Ambrosio, M.R.; Rossi, R.; Bagni, B.; Pansini, R.; degli Uberti, E.C. Circadian rhythm of calcitonin gene-related peptide in uncomplicated essential hypertension. J. Hypertens. 1992, 10, 1227–1234. [Google Scholar] [CrossRef]
  21. Wang, F.; Deng, Y.; Wang, J.; Yu, L.; Ding, F.; Lian, W.; Liu, Q.; Lin, X. The PLGA nanoparticles for sustainable release of CGRP to ameliorate the inflammatory and vascular disorders in the lung of CGRP-deficient rats. Drug Deliv. 2021, 28, 865–872. [Google Scholar] [CrossRef] [PubMed]
  22. Sohn, I.; Sheykhzade, M.; Edvinsson, L.; Sams, A. The effects of CGRP in vascular tissue—Classical vasodilation, shadowed effects and systemic dilemmas. Eur. J. Pharmacol. 2020, 881, 173205. [Google Scholar] [CrossRef] [PubMed]
  23. Smillie, S.J.; King, R.; Kodji, X.; Outzen, E.; Pozsgai, G.; Fernandes, E.; Marshall, N.; de Winter, P.; Heads, R.J.; Dessapt-Baradez, C.; et al. An ongoing role of α-calcitonin gene-related peptide as part of a protective network against hypertension, vascular hypertrophy, and oxidative stress. Hypertension 2014, 63, 1056–1062. [Google Scholar] [CrossRef]
  24. Petersen, K.A.; Birk, S.; Lassen, L.H.; Kruuse, C.; Jonassen, O.; Lesko, L.; Olesen, J. The CGRP-antagonist, BIBN4096BS does not affect cerebral or systemic haemodynamics in healthy volunteers. Cephalalgia 2005, 25, 139–147. [Google Scholar] [CrossRef]
  25. Ichikawa, H.; Matsuo, S.; Wakisaka, S.; Akai, M. Fine structure of calcitonin gene-related peptide-immunoreactive nerve fibres in the rat temporomandibular joint. Arch. Oral Biol. 1990, 35, 727–730. [Google Scholar] [CrossRef] [PubMed]
  26. Neychev, D.; Sbirkova, T.; Ivanovska, M.; Raycheva, R.; Murdjeva, M.; Atanasov, D. Correlation between CGRP Levels and the Neuropathic and Inflammatory Component of Postoperative Pain. Folia Med. 2020, 62, 365–371. [Google Scholar] [CrossRef] [PubMed]
  27. Schou, W.S.; Ashina, S.; Amin, F.M.; Goadsby, P.J.; Ashina, M. Calcitonin gene-related peptide and pain: A systematic review. J. Headache Pain 2017, 18, 34. [Google Scholar] [CrossRef] [PubMed]
  28. Nakamura-Craig, M.; Gill, B.K. Effect of neurokinin A, substance P and calcitonin gene related peptide in peripheral hyperalgesia in the rat paw. Neurosci. Lett. 1991, 124, 49–51. [Google Scholar] [CrossRef]
  29. Mogil, J.S.; Miermeister, F.; Seifert, F.; Strasburg, K.; Zimmermann, K.; Reinold, H.; Austin, J.S.; Bernardini, N.; Chesler, E.J.; Hofmann, H.A.; et al. Variable sensitivity to noxious heat is mediated by differential expression of the CGRP gene. Proc. Natl. Acad. Sci. USA 2005, 102, 12938–12943. [Google Scholar] [CrossRef]
  30. Iyengar, S.; Johnson, K.W.; Ossipov, M.H.; Aurora, S.K. CGRP and the Trigeminal System in Migraine. Headache 2019, 59, 659–681. [Google Scholar] [CrossRef]
  31. Russo, A.F. Calcitonin gene-related peptide (CGRP): A new target for migraine. Annu. Rev. Pharmacol. Toxicol. 2015, 55, 533–552. [Google Scholar] [CrossRef] [PubMed]
  32. Russo, A.F.; Hay, D.L. CGRP physiology, pharmacology, and therapeutic targets: Migraine and beyond. Physiol. Rev. 2023, 103, 1565–1644. [Google Scholar] [CrossRef] [PubMed]
  33. Edvinsson, L.; Haanes, K.A.; Warfvinge, K.; Krause, D.N. CGRP as the target of new migraine therapies—successful translation from bench to clinic. Nat Rev Neurol 2018, 14, 338–350. [Google Scholar] [CrossRef]
  34. Sánchez-Robles, E.M.; Girón, R.; Paniagua, N.; Rodríguez-Rivera, C.; Pascual, D.; Goicoechea, C. Monoclonal Antibodies for Chronic Pain Treatment: Present and Future. Int. J. Mol. Sci. 2021, 22, 10325. [Google Scholar] [CrossRef]
  35. Doods, H.; Hallermayer, G.; Wu, D.; Entzeroth, M.; Rudolf, K.; Engel, W.; Eberlein, W. Pharmacological profile of BIBN4096BS, the first selective small molecule CGRP antagonist. Br. J. Pharmacol. 2000, 129, 420–423. [Google Scholar] [CrossRef]
  36. Paone, D.V.; Shaw, A.W.; Nguyen, D.N.; Burgey, C.S.; Deng, J.Z.; Kane, S.A.; Koblan, K.S.; Salvatore, C.A.; Mosser, S.D.; Johnston, V.K.; et al. Potent, orally bioavailable calcitonin gene-related peptide receptor antagonists for the treatment of migraine: Discovery of N-[(3R,6S)-6-(2,3-difluorophenyl)-2-oxo-1- (2,2,2-trifluoroethyl)azepan-3-yl]-4- (2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin- 1-yl)piperidine-1-carboxamide (MK-0974). J. Med. Chem. 2007, 50, 5564–5567. [Google Scholar]
  37. Hewitt, D.J.; Aurora, S.K.; Dodick, D.W.; Goadsby, P.J.; Ge, Y.J.; Bachman, R.; Taraborelli, D.; Fan, X.; Assaid, C.; Lines, C.; et al. Randomized controlled trial of the CGRP receptor antagonist MK-3207 in the acute treatment of migraine. Cephalalgia 2011, 31, 712–722. [Google Scholar] [CrossRef]
  38. Croop, R.; Madonia, J.; Stock, D.A.; Thiry, A.; Forshaw, M.; Murphy, A.; Coric, V.; Lipton, R.B. Zavegepant nasal spray for the acute treatment of migraine: A Phase 2/3 double-blind, randomized, placebo-controlled, dose-ranging trial. Headache 2022, 62, 1153–1163. [Google Scholar] [CrossRef]
  39. Diener, H.C.; Barbanti, P.; Dahlöf, C.; Reuter, U.; Habeck, J.; Podhorna, J. BI 44370 TA, an oral CGRP antagonist for the treatment of acute migraine attacks: Results from a phase II study. Cephalalgia 2011, 31, 573–584. [Google Scholar] [CrossRef]
  40. Markham, A. Erenumab: First Global Approval. Drugs 2018, 78, 1157–1161. [Google Scholar] [CrossRef]
  41. Scott, L.J. Rimegepant: First Approval. Drugs 2020, 80, 741–746. [Google Scholar] [CrossRef] [PubMed]
  42. Scott, L.J. Ubrogepant: First Approval. Drugs 2020, 80, 323–328. [Google Scholar] [CrossRef] [PubMed]
  43. Deeks, E.D. Atogepant: First Approval. Drugs 2022, 82, 65–70. [Google Scholar] [CrossRef] [PubMed]
  44. Lamb, Y.N. Galcanezumab: First Global Approval. Drugs 2018, 78, 1769–1775. [Google Scholar] [CrossRef] [PubMed]
  45. Hoy, S.M. Fremanezumab: First Global Approval. Drugs 2018, 78, 1829–1834. [Google Scholar] [CrossRef]
  46. Dhillon, S. Eptinezumab: First Approval. Drugs 2020, 80, 733–739. [Google Scholar] [CrossRef]
  47. Smillie, S.J.; Brain, S.D. Calcitonin gene-related peptide (CGRP) and its role in hypertension. Neuropeptides 2011, 45, 93–104. [Google Scholar] [CrossRef]
  48. Sun, L.; Wang, G.; He, M.; Mei, Z.; Zhang, F.; Liu, P. Effect and mechanism of the CACNA2D1-CGRP pathway in osteoarthritis-induced ongoing pain. Biomed. Pharmacother. 2020, 129, 110374. [Google Scholar] [CrossRef]
  49. Bjurholm, A.; Kreicbergs, A.; Brodin, E.; Schultzberg, M. Substance P- and CGRP-immunoreactive nerves in bone. Peptides 1988, 9, 165–171. [Google Scholar] [CrossRef]
  50. Haegerstrand, A.; Dalsgaard, C.J.; Jonzon, B.; Larsson, O.; Nilsson, J. Calcitonin gene-related peptide stimulates proliferation of human endothelial cells. Proc. Natl. Acad. Sci. USA 1990, 87, 3299–3303. [Google Scholar] [CrossRef]
  51. Hosoi, J.; Murphy, G.F.; Egan, C.L.; Lerner, E.A.; Grabbe, S.; Asahina, A.; Granstein, R.D. Regulation of Langerhans cell function by nerves containing calcitonin gene-related peptide. Nature 1993, 363, 159–163. [Google Scholar] [CrossRef] [PubMed]
  52. Naot, D.; Cornish, J. The role of peptides and receptors of the calcitonin family in the regulation of bone metabolism. Bone 2008, 43, 813–818. [Google Scholar] [CrossRef] [PubMed]
  53. Chrissobolis, S.; Zhang, Z.; Kinzenbaw, D.A.; Lynch, C.M.; Russo, A.F.; Faraci, F.M. Receptor activity-modifying protein-1 augments cerebrovascular responses to calcitonin gene-related peptide and inhibits angiotensin II-induced vascular dysfunction. Stroke 2010, 41, 2329–2334. [Google Scholar] [CrossRef] [PubMed]
  54. Li, H.; Qu, J.; Zhu, H.; Wang, J.; He, H.; Xie, X.; Wu, R.; Lu, Q. Corrigendum: CGRP Regulates the Age-Related Switch Between Osteoblast and Adipocyte Differentiation. Front Cell Dev. Biol. 2021, 9, 715740. [Google Scholar] [CrossRef]
  55. Pajarinen, J.; Lin, T.; Gibon, E.; Kohno, Y.; Maruyama, M.; Nathan, K.; Lu, L.; Yao, Z.; Goodman, S.B. Mesenchymal stem cell-macrophage crosstalk and bone healing. Biomaterials 2019, 196, 80–89. [Google Scholar] [CrossRef]
  56. Marrella, A.; Lee, T.Y.; Lee, D.H.; Karuthedom, S.; Syla, D.; Chawla, A.; Khademhosseini, A.; Jang, H.L. Engineering vascularized and innervated bone biomaterials for improved skeletal tissue regeneration. Mater. Today 2018, 21, 362–376. [Google Scholar] [CrossRef]
  57. Brazill, J.M.; Beeve, A.T.; Craft, C.S.; Ivanusic, J.J.; Scheller, E.L. Nerves in Bone: Evolving Concepts in Pain and Anabolism. J. Bone Miner. Res. 2019, 34, 1393–1406. [Google Scholar] [CrossRef]
  58. Ballica, R.; Valentijn, K.; Khachatryan, A.; Guerder, S.; Kapadia, S.; Gundberg, C.; Gilligan, J.; Flavell, R.A.; Vignery, A. Targeted expression of calcitonin gene-related peptide to osteoblasts increases bone density in mice. J. Bone Miner. Res. 1999, 14, 1067–1074. [Google Scholar] [CrossRef]
  59. Schinke, T.; Liese, S.; Priemel, M.; Haberland, M.; Schilling, A.F.; Catala-Lehnen, P.; Blicharski, D.; Rueger, J.M.; Gagel, R.F.; Emeson, R.B.; et al. Decreased bone formation and osteopenia in mice lacking alpha-calcitonin gene-related peptide. J. Bone Miner. Res. 2004, 19, 2049–2056. [Google Scholar] [CrossRef]
  60. Hukkanen, M.; Konttinen, Y.T.; Rees, R.G.; Gibson, S.J.; Santavirta, S.; Polak, J.M. Innervation of bone from healthy and arthritic rats by substance P and calcitonin gene related peptide containing sensory fibers. J. Rheumatol. 1992, 19, 1252–1259. [Google Scholar]
  61. Hu, B.; Lv, X.; Wei, L.; Wang, Y.; Zheng, G.; Yang, C.; Zang, F.; Wang, J.; Li, J.; Wu, X.; et al. Sensory Nerve Maintains Intervertebral Disc Extracellular Matrix Homeostasis Via CGRP/CHSY1 Axis. Adv. Sci. (Weinh) 2022, 9, e2202620. [Google Scholar] [CrossRef]
  62. Vignery, A.; McCarthy, T.L. The neuropeptide calcitonin gene-related peptide stimulates insulin-like growth factor I production by primary fetal rat osteoblasts. Bone 1996, 18, 331–335. [Google Scholar] [CrossRef]
  63. Liang, W.; Zhuo, X.; Tang, Z.; Wei, X.; Li, B. Calcitonin gene-related peptide stimulates proliferation and osteogenic differentiation of osteoporotic rat-derived bone mesenchymal stem cells. Mol. Cell. Biochem. 2015, 402, 101–110. [Google Scholar] [CrossRef]
  64. He, H.; Chai, J.; Zhang, S.; Ding, L.; Yan, P.; Du, W.; Yang, Z. CGRP may regulate bone metabolism through stimulating osteoblast differentiation and inhibiting osteoclast formation. Mol. Med. Rep. 2016, 13, 3977–3984. [Google Scholar] [CrossRef]
  65. Elefteriou, F.; Ahn, J.D.; Takeda, S.; Starbuck, M.; Yang, X.; Liu, X.; Kondo, H.; Richards, W.G.; Bannon, T.W.; Noda, M.; et al. Leptin regulation of bone resorption by the sympathetic nervous system and CART. Nature 2005, 434, 514–520. [Google Scholar] [CrossRef] [PubMed]
  66. Komori, T. Functions of Osteocalcin in Bone, Pancreas, Testis, and Muscle. Int. J. Mol. Sci. 2020, 21, 7513. [Google Scholar] [CrossRef]
  67. Wang, Y.; Xia, C.; Chen, Y.; Jiang, T.; Hu, Y.; Gao, Y. Resveratrol Synergistically Promotes BMP9-Induced Osteogenic Differentiation of Mesenchymal Stem Cells. Stem Cells Int. 2022, 2022, 8124085. [Google Scholar] [CrossRef] [PubMed]
  68. Tsuji, K.; Bandyopadhyay, A.; Harfe, B.D.; Cox, K.; Kakar, S.; Gerstenfeld, L.; Einhorn, T.; Tabin, C.J.; Rosen, V. BMP2 activity, although dispensable for bone formation, is required for the initiation of fracture healing. Nat. Genet. 2006, 38, 1424–1429. [Google Scholar] [CrossRef]
  69. Rosen, V. BMP2 signaling in bone development and repair. Cytokine Growth Factor Rev. 2009, 20, 475–480. [Google Scholar] [CrossRef] [PubMed]
  70. Jiang, F.; Qi, X.; Wu, X.; Lin, S.; Shi, J.; Zhang, W.; Jiang, X. Regulating macrophage-MSC interaction to optimize BMP-2-induced osteogenesis in the local microenvironment. Bioact. Mater 2023, 25, 307–318. [Google Scholar] [CrossRef] [PubMed]
  71. Tian, G.; Zhang, G.; Tan, Y.H. Calcitonin gene-related peptide stimulates BMP-2 expression and the differentiation of human osteoblast-like cells in vitro. Acta Pharmacol. Sin. 2013, 34, 1467–1474. [Google Scholar] [CrossRef]
  72. Wang, L.; Shi, X.; Zhao, R.; Halloran, B.P.; Clark, D.J.; Jacobs, C.R.; Kingery, W.S. Calcitonin-gene-related peptide stimulates stromal cell osteogenic differentiation and inhibits RANKL induced NF-kappaB activation, osteoclastogenesis and bone resorption. Bone 2010, 46, 1369–1379. [Google Scholar] [CrossRef] [PubMed]
  73. Jia, S.; Zhang, S.J.; Wang, X.D.; Yang, Z.H.; Sun, Y.N.; Gupta, A.; Hou, R.; Lei, D.L.; Hu, K.J.; Ye, W.M.; et al. Calcitonin gene-related peptide enhances osteogenic differentiation and recruitment of bone marrow mesenchymal stem cells in rats. Exp. Ther. Med. 2019, 18, 1039–1046. [Google Scholar] [CrossRef]
  74. Zhou, R.; Yuan, Z.; Liu, J.; Liu, J. Calcitonin gene-related peptide promotes the expression of osteoblastic genes and activates the WNT signal transduction pathway in bone marrow stromal stem cells. Mol. Med. Rep. 2016, 13, 4689–4696. [Google Scholar] [CrossRef]
  75. Zhang, Y.; Xu, J.; Ruan, Y.C.; Yu, M.K.; O’Laughlin, M.; Wise, H.; Chen, D.; Tian, L.; Shi, D.; Wang, J.; et al. Implant-derived magnesium induces local neuronal production of CGRP to improve bone-fracture healing in rats. Nat. Med. 2016, 22, 1160–1169. [Google Scholar] [CrossRef]
  76. Appelt, J.; Baranowsky, A.; Jahn, D.; Yorgan, T.; Köhli, P.; Otto, E.; Farahani, S.K.; Graef, F.; Fuchs, M.; Herrera, A.; et al. The neuropeptide calcitonin gene-related peptide alpha is essential for bone healing. EBioMedicine 2020, 59, 102970. [Google Scholar] [CrossRef] [PubMed]
  77. Onuoha, G.N.; Alpar, E.K. Elevation of plasma CGRP and SP levels in orthopedic patients with fracture neck of femur. Neuropeptides 2000, 34, 116–120. [Google Scholar] [CrossRef]
  78. Takahashi, N.; Matsuda, Y.; Sato, K.; de Jong, P.R.; Bertin, S.; Tabeta, K.; Yamazaki, K. Neuronal TRPV1 activation regulates alveolar bone resorption by suppressing osteoclastogenesis via CGRP. Sci. Rep. 2016, 6, 29294. [Google Scholar] [CrossRef] [PubMed]
  79. Ishizuka, K.; Hirukawa, K.; Nakamura, H.; Togari, A. Inhibitory effect of CGRP on osteoclast formation by mouse bone marrow cells treated with isoproterenol. Neurosci. Lett. 2005, 379, 47–51. [Google Scholar] [CrossRef]
  80. Akopian, A.; Demulder, A.; Ouriaghli, F.; Corazza, F.; Fondu, P.; Bergmann, P. Effects of CGRP on human osteoclast-like cell formation: A possible connection with the bone loss in neurological disorders. Peptides 2000, 21, 559–564. [Google Scholar] [CrossRef]
  81. Toda, M.; Suzuki, T.; Hosono, K.; Kurihara, Y.; Kurihara, H.; Hayashi, I.; Kitasato, H.; Hoka, S.; Majima, M. Roles of calcitonin gene-related peptide in facilitation of wound healing and angiogenesis. Biomed. Pharmacother. 2008, 62, 352–359. [Google Scholar] [CrossRef]
  82. Aoki, M.; Tamai, K.; Saotome, K. Substance P- and calcitonin gene-related peptide-immunofluorescent nerves in the repair of experimental bone defects. Int. Orthop. 1994, 18, 317–324. [Google Scholar] [CrossRef] [PubMed]
  83. Liu, W.C.; Chen, S.; Zheng, L.; Qin, L. Angiogenesis Assays for the Evaluation of Angiogenic Properties of Orthopaedic Biomaterials - A General Review. Adv. Healthc. Mater. 2017, 6, 1600434. [Google Scholar] [CrossRef]
  84. Maeda, Y.; Miwa, Y.; Sato, I. Expression of CGRP, vasculogenesis and osteogenesis associated mRNAs in the developing mouse mandible and tibia. Eur. J. Histochem. 2017, 61, 2750. [Google Scholar] [CrossRef] [PubMed]
  85. Bidegain, M.; Roos, B.A.; Hill, E.L.; Howard, G.A.; Balkan, W. Calcitonin gene-related peptide (CGRP) in the developing mouse limb. Endocr. Res. 1995, 21, 743–755. [Google Scholar] [CrossRef] [PubMed]
  86. Mi, J.; Xu, J.; Yao, H.; Li, X.; Tong, W.; Li, Y.; Dai, B.; He, X.; Chow, D.; Li, G.; et al. Calcitonin Gene-Related Peptide Enhances Distraction Osteogenesis by Increasing Angiogenesis. Tissue Eng. Part A 2021, 27, 87–102. [Google Scholar] [CrossRef]
  87. Zheng, S.; Li, W.; Xu, M.; Bai, X.; Zhou, Z.; Han, J.; Shyy, J.Y.; Wang, X. Calcitonin gene-related peptide promotes angiogenesis via AMP-activated protein kinase. Am. J. Physiol. Cell Physiol. 2010, 299, C1485–C1492. [Google Scholar] [CrossRef] [PubMed]
  88. Mapp, P.I.; McWilliams, D.F.; Turley, M.J.; Hargin, E.; Walsh, D.A. A role for the sensory neuropeptide calcitonin gene-related peptide in endothelial cell proliferation in vivo. Br. J. Pharmacol. 2012, 166, 1261–1271. [Google Scholar] [CrossRef]
  89. Toda, M.; Suzuki, T.; Hosono, K.; Hayashi, I.; Hashiba, S.; Onuma, Y.; Amano, H.; Kurihara, Y.; Kurihara, H.; Okamoto, H.; et al. Neuronal system-dependent facilitation of tumor angiogenesis and tumor growth by calcitonin gene-related peptide. Proc. Natl. Acad. Sci. USA 2008, 105, 13550–13555. [Google Scholar] [CrossRef]
  90. Wu, J.; Liu, S.; Wang, Z.; Ma, S.; Meng, H.; Hu, J. Calcitonin gene-related peptide promotes proliferation and inhibits apoptosis in endothelial progenitor cells via inhibiting MAPK signaling. Proteome Sci. 2018, 16, 18. [Google Scholar] [CrossRef]
  91. Bo, Y.; Yan, L.; Gang, Z.; Tao, L.; Yinghui, T. Effect of calcitonin gene-related peptide on osteoblast differentiation in an osteoblast and endothelial cell co-culture system. Cell Biol. Int. 2012, 36, 909–915. [Google Scholar] [CrossRef] [PubMed]
  92. Zhu, W.Y.; Guo, J.; Yang, W.F.; Tao, Z.Y.; Lan, X.; Wang, L.; Xu, J.; Qin, L.; Su, Y.X. Biodegradable magnesium implant enhances angiogenesis and alleviates medication-related osteonecrosis of the jaw in rats. J. Orthop. Translat. 2022, 33, 153–161. [Google Scholar] [CrossRef] [PubMed]
  93. Guo, Y.; Chen, H.; Jiang, Y.; Yuan, Y.; Zhang, Q.; Guo, Q.; Gong, P. CGRP regulates the dysfunction of peri-implant angiogenesis and osseointegration in streptozotocin-induced diabetic rats. Bone 2020, 139, 115464. [Google Scholar] [CrossRef] [PubMed]
  94. Li, Y.; Xu, J.; Mi, J.; He, X.; Pan, Q.; Zheng, L.; Zu, H.; Chen, Z.; Dai, B.; Li, X.; et al. Biodegradable magnesium combined with distraction osteogenesis synergistically stimulates bone tissue regeneration via CGRP-FAK-VEGF signaling axis. Biomaterials 2021, 275, 120984. [Google Scholar] [CrossRef]
  95. Brown, B.N.; Badylak, S.F. Expanded applications, shifting paradigms and an improved understanding of host-biomaterial interactions. Acta Biomater. 2013, 9, 4948–4955. [Google Scholar] [CrossRef]
  96. Gibon, E.; Lu, L.; Goodman, S.B. Aging, inflammation, stem cells, and bone healing. Stem Cell Res. Ther. 2016, 7, 44. [Google Scholar] [CrossRef]
  97. Yang, L.; Sakurai, T.; Kamiyoshi, A.; Ichikawa-Shindo, Y.; Kawate, H.; Yoshizawa, T.; Koyama, T.; Iesato, Y.; Uetake, R.; Yamauchi, A.; et al. Endogenous CGRP protects against neointimal hyperplasia following wire-induced vascular injury. J. Mol. Cell. Cardiol. 2013, 59, 55–66. [Google Scholar] [CrossRef]
  98. Feng, Y.; Tang, Y.; Guo, J.; Wang, X. Inhibition of LPS-induced TNF-alpha production by calcitonin gene-related peptide (CGRP) in cultured mouse peritoneal macrophages. Life Sci. 1997, 61, PL 281–PL 287. [Google Scholar] [CrossRef]
  99. Millet, I.; Vignery, A. The neuropeptide calcitonin gene-related peptide inhibits TNF-alpha but poorly induces IL-6 production by fetal rat osteoblasts. Cytokine 1997, 9, 999–1007. [Google Scholar] [CrossRef]
  100. Niedermair, T.; Straub, R.H.; Brochhausen, C.; Grässel, S. Impact of the Sensory and Sympathetic Nervous System on Fracture Healing in Ovariectomized Mice. Int. J. Mol. Sci. 2020, 21, 405. [Google Scholar] [CrossRef]
  101. Loi, F.; Córdova, L.A.; Zhang, R.; Pajarinen, J.; Lin, T.H.; Goodman, S.B.; Yao, Z. The effects of immunomodulation by macrophage subsets on osteogenesis in vitro. Stem. Cell Res. Ther. 2016, 7, 15. [Google Scholar] [CrossRef] [PubMed]
  102. Yuan, Y.; Jiang, Y.; Wang, B.; Guo, Y.; Gong, P.; Xiang, L. Deficiency of Calcitonin Gene-Related Peptide Affects Macrophage Polarization in Osseointegration. Front Physiol. 2020, 11, 733. [Google Scholar] [CrossRef] [PubMed]
  103. Zhang, Q.; Wu, B.; Yuan, Y.; Zhang, X.; Guo, Y.; Gong, P.; Xiang, L. CGRP-modulated M2 macrophages regulate osteogenesis of MC3T3-E1 via Yap1. Arch. Biochem. Biophys. 2021, 697, 108697. [Google Scholar] [CrossRef] [PubMed]
  104. Maruyama, M.; Rhee, C.; Utsunomiya, T.; Zhang, N.; Ueno, M.; Yao, Z.; Goodman, S.B. Modulation of the Inflammatory Response and Bone Healing. Front. Endocrinol. (Lausanne) 2020, 11, 386. [Google Scholar] [CrossRef]
  105. Chen, J.; Ma, G.; Liu, W.; Liu, Y.; Ding, Y. The influence of the sensory neurotransmitter calcitonin gene-related peptide on bone marrow mesenchymal stem cells from ovariectomized rats. J. Bone Miner. Metab. 2017, 35, 473–484. [Google Scholar] [CrossRef]
  106. Zhang, Q.; Guo, Y.; Yu, H.; Tang, Y.; Yuan, Y.; Jiang, Y.; Chen, H.; Gong, P.; Xiang, L. Receptor activity-modifying protein 1 regulates the phenotypic expression of BMSCs via the Hippo/Yap pathway. J. Cell. Physiol. 2019, 234, 13969–13976. [Google Scholar] [CrossRef]
  107. Michelangeli, V.P.; Fletcher, A.E.; Allan, E.H.; Nicholson, G.C.; Martin, T.J. Effects of calcitonin gene-related peptide on cyclic AMP formation in chicken, rat, and mouse bone cells. J. Bone Miner. Res. 1989, 4, 269–272. [Google Scholar] [CrossRef]
  108. Villa, I.; Melzi, R.; Pagani, F.; Ravasi, F.; Rubinacci, A.; Guidobono, F. Effects of calcitonin gene-related peptide and amylin on human osteoblast-like cells proliferation. Eur. J. Pharmacol. 2000, 409, 273–278. [Google Scholar] [CrossRef]
  109. Mrak, E.; Guidobono, F.; Moro, G.; Fraschini, G.; Rubinacci, A.; Villa, I. Calcitonin gene-related peptide (CGRP) inhibits apoptosis in human osteoblasts by β-catenin stabilization. J. Cell. Physiol. 2010, 225, 701–708. [Google Scholar] [CrossRef]
  110. Owan, I.; Ibaraki, K. The role of calcitonin gene-related peptide (CGRP) in macrophages: The presence of functional receptors and effects on proliferation and differentiation into osteoclast-like cells. Bone Miner. 1994, 24, 151–164. [Google Scholar] [CrossRef]
  111. Yoo, Y.M.; Kwag, J.H.; Kim, K.H.; Kim, C.H. Effects of neuropeptides and mechanical loading on bone cell resorption in vitro. Int. J. Mol. Sci. 2014, 15, 5874–5883. [Google Scholar] [CrossRef] [PubMed]
  112. Calland, J.W.; Harris, S.E.; Carnes, D.L., Jr. Human pulp cells respond to calcitonin gene-related peptide in vitro. J. Endod. 1997, 23, 485–489. [Google Scholar] [CrossRef] [PubMed]
  113. Fang, Z.; Yang, Q.; Xiong, W.; Li, G.H.; Liao, H.; Xiao, J.; Li, F. Effect of CGRP-adenoviral vector transduction on the osteoblastic differentiation of rat adipose-derived stem cells. PLoS ONE 2013, 8, e72738. [Google Scholar] [CrossRef] [PubMed]
  114. Seifert, H.; Sawchenko, P.; Chesnut, J.; Rivier, J.; Vale, W.; Pandol, S.J. Receptor for calcitonin gene-related peptide: Binding to exocrine pancreas mediates biological actions. Am. J. Physiol. 1985, 249, G147–G151. [Google Scholar] [CrossRef]
  115. Edvinsson, L.; Fredholm, B.B.; Hamel, E.; Jansen, I.; Verrecchia, C. Perivascular peptides relax cerebral arteries concomitant with stimulation of cyclic adenosine monophosphate accumulation or release of an endothelium-derived relaxing factor in the cat. Neurosci. Lett. 1985, 58, 213–217. [Google Scholar] [CrossRef]
  116. Takamori, M.; Yoshikawa, H. Effect of calcitonin gene-related peptide on skeletal muscle via specific binding site and G protein. J. Neurol. Sci. 1989, 90, 99–109. [Google Scholar] [CrossRef]
  117. Main, M.J.; Brown, J.; Brown, S.; Fraser, N.J.; Foord, S.M. The CGRP receptor can couple via pertussis toxin sensitive and insensitive G proteins. FEBS Lett. 1998, 441, 6–10. [Google Scholar] [CrossRef]
  118. Dickerson, I.M. Role of CGRP-receptor component protein (RCP) in CLR/RAMP function. Curr. Protein Pept. Sci. 2013, 14, 407–415. [Google Scholar] [CrossRef]
  119. Cottrell, G.S. CGRP Receptor Signalling Pathways. Handb. Exp. Pharmacol. 2019, 255, 37–64. [Google Scholar]
  120. Weston, C.; Winfield, I.; Harris, M.; Hodgson, R.; Shah, A.; Dowell, S.J.; Mobarec, J.C.; Woodlock, D.A.; Reynolds, C.A.; Poyner, D.R.; et al. Receptor Activity-modifying Protein-directed G Protein Signaling Specificity for the Calcitonin Gene-related Peptide Family of Receptors. J. Biol. Chem. 2016, 291, 21925–21944. [Google Scholar] [CrossRef]
  121. Hankenson, K.D.; Gagne, K.; Shaughnessy, M. Extracellular signaling molecules to promote fracture healing and bone regeneration. Adv. Drug Deliv. Rev. 2015, 94, 3–12. [Google Scholar] [CrossRef] [PubMed]
  122. Hoff, A.O.; Catala-Lehnen, P.; Thomas, P.M.; Priemel, M.; Rueger, J.M.; Nasonkin, I.; Bradley, A.; Hughes, M.R.; Ordonez, N.; Cote, G.J.; et al. Increased bone mass is an unexpected phenotype associated with deletion of the calcitonin gene. J. Clin. Invest. 2002, 110, 1849–1857. [Google Scholar] [CrossRef] [PubMed]
  123. Kauther, M.D.; Neuerburg, C.; Wefelnberg, F.; Bachmann, H.S.; Schlepper, R.; Hilken, G.; Broecker-Preuss, M.; Grabellus, F.; Schilling, A.F.; Jäger, M.; et al. RANKL-associated suppression of particle-induced osteolysis in an aged model of Calcitonin and α-CGRP deficiency. Biomaterials 2013, 34, 2911–2919. [Google Scholar] [CrossRef] [PubMed]
  124. Liang, W.; Li, L.; Cui, X.; Tang, Z.; Wei, X.; Pan, H.; Li, B. Enhanced proliferation and differentiation effects of a CGRP- and Sr-enriched calcium phosphate cement on bone mesenchymal stem cells. J. Appl. Biomater. Funct. Mater. 2016, 14, e431–e440. [Google Scholar] [CrossRef]
  125. Yu, X.; Liu, S.; Chen, X.; Du, Y.; Yin, X.; Du, Y.; Li, S. Calcitonin gene related peptide gene-modified rat bone mesenchymal stem cells are effective seed cells in tissue engineering to repair skull defects. Histol. Histopathol. 2019, 34, 1229–1241. [Google Scholar]
  126. Irie, K.; Hara-Irie, F.; Ozawa, H.; Yajima, T. Calcitonin gene-related peptide (CGRP)-containing nerve fibers in bone tissue and their involvement in bone remodeling. Microsc. Res. Tech. 2002, 58, 85–90. [Google Scholar] [CrossRef]
  127. Gao, F.; Lv, T.R.; Zhou, J.C.; Qin, X.D. Effects of obesity on the healing of bone fracture in mice. J. Orthop Surg Res. 2018, 13, 145. [Google Scholar] [CrossRef]
  128. Yang, Y.; Zhang, B.; Yang, Y.; Peng, B.; Ye, R. PLGA Containing Human Adipose-Derived Stem Cell-Derived Extracellular Vesicles Accelerates the Repair of Alveolar Bone Defects via Transfer of CGRP. Oxid. Med. Cell Longev. 2022, 2022, 4815284. [Google Scholar] [CrossRef]
  129. Zhao, D.; Witte, F.; Lu, F.; Wang, J.; Li, J.; Qin, L. Current status on clinical applications of magnesium-based orthopaedic implants: A review from clinical translational perspective. Biomaterials 2017, 112, 287–302. [Google Scholar] [CrossRef]
  130. Ding, Y.; Yan, Q.; Ruan, J.W.; Zhang, Y.Q.; Li, W.J.; Zhang, Y.J.; Li, Y.; Dong, H.; Zeng, Y.S. Electro-acupuncture promotes survival, differentiation of the bone marrow mesenchymal stem cells as well as functional recovery in the spinal cord-transected rats. BMC Neurosci. 2009, 10, 35. [Google Scholar] [CrossRef]
  131. Bucelli, R.C.; Gonsiorek, E.A.; Kim, W.Y.; Bruun, D.; Rabin, R.A.; Higgins, D.; Lein, P.J. Statins decrease expression of the proinflammatory neuropeptides calcitonin gene-related peptide and substance P in sensory neurons. J. Pharmacol. Exp. Ther. 2008, 324, 1172–1180. [Google Scholar] [CrossRef] [PubMed]
  132. Tuzmen, C.; Campbell, P.G. Crosstalk between neuropeptides SP and CGRP in regulation of BMP2-induced bone differentiation. Connect. Tissue Res. 2018, 59, 81–90. [Google Scholar] [CrossRef] [PubMed]
  133. Edvinsson, L. Role of CGRP in Migraine. Handb. Exp. Pharmacol. 2019, 255, 121–130. [Google Scholar]
  134. Sharma, K.; Sharma, K.K.; Sharma, A.; Jain, R. Peptide-based drug discovery: Current status and recent advances. Drug Discov. Today 2023, 28, 103464. [Google Scholar] [CrossRef]
  135. Fosgerau, K.; Hoffmann, T. Peptide therapeutics: Current status and future directions. Drug Discov. Today 2015, 20, 122–128. [Google Scholar] [CrossRef]
Biomolecules 13 00838 g001 550
Figure 1. CGRP regulates various cells to promote bone repair. CGRP is secreted by sensory nerve cells, and its effects on bone tissue are: 1. CGRP can bind to the CLR receptor on the cell surface to directly enhance the osteoblast and osteogenic gene expression; 2. CGRP can inhibit the RANKL/RANK/NF-κB pathway by increasing OPG level, inhibiting osteoclast proliferation, and reducing the osteoclast effect; 3. CGRP can enhance the angiogenesis of vascular endothelial cells by promoting the expression of VEGF and HIF factors, induce angiogenesis, and provide nutritional support for bone repair; 4. CGRP can enhance the transformation of M0 into M2 macrophages and regulate the immune microenvironment of bone repair. CGRP is a calcitonin gene-related peptide, CLR is a calcein gene-related peptide receptor, RANK is the receptor activator of nuclear factor kappa B, RANKL is the receptor activator of nuclear factor kappa B ligand, OPG is osteoprotegerin, HIF is a hypoxia-inducible factor, and VEGF is a vascular endothelial growth factor.
Figure 1. CGRP regulates various cells to promote bone repair. CGRP is secreted by sensory nerve cells, and its effects on bone tissue are: 1. CGRP can bind to the CLR receptor on the cell surface to directly enhance the osteoblast and osteogenic gene expression; 2. CGRP can inhibit the RANKL/RANK/NF-κB pathway by increasing OPG level, inhibiting osteoclast proliferation, and reducing the osteoclast effect; 3. CGRP can enhance the angiogenesis of vascular endothelial cells by promoting the expression of VEGF and HIF factors, induce angiogenesis, and provide nutritional support for bone repair; 4. CGRP can enhance the transformation of M0 into M2 macrophages and regulate the immune microenvironment of bone repair. CGRP is a calcitonin gene-related peptide, CLR is a calcein gene-related peptide receptor, RANK is the receptor activator of nuclear factor kappa B, RANKL is the receptor activator of nuclear factor kappa B ligand, OPG is osteoprotegerin, HIF is a hypoxia-inducible factor, and VEGF is a vascular endothelial growth factor.
Biomolecules 13 00838 g001
Biomolecules 13 00838 g002 550
Figure 2. CGRP cellular pathway. CGRP transmits signals to the cell using the G protein-coupled receptor-CLR-RAMP1 dimer: 1. cAMP signaling pathway: activates the G protein and AC to increase the intracellular second messenger. cAMP concentration activates PKA and CREB and promotes mRNA transcription in the nucleus. 2. Phosphatidylinositol signaling pathway: by activating PLCβ1, hydrolyzing PIP2 to generate second messengers, IP3 and DAG. IP3 is gated with the IP3 ligand on the endoplasmic reticulum. Calcium channel binding elevates the intracellular Ca2+ concentration and activates various calcium ion-dependent proteins. DAG rivets on the cell membrane to activate PKC bound to the cell membrane. Moreover, intracellular free PKC can phosphorylate the serine/threonine residues of proteins and have a biological effect. AC is adenylate cyclase. cAMP is cyclic adenosine monophosphate, PKA is protein kinase A, CREB is cyclic adenosine monophosphate response element binding protein, PLCβ1 is the phospholipase C, β1, IP3 is inositol 1,4,5-triphosphate, DAG is the diacylglycerol, PIP2 is the phosphatidylinositol-4,5-bisphosphate, PKC is a protein kinase C, CGRP is a calcitonin gene-related peptide, CLR is a calcitonin gene-related Peptide receptor, RAMP1 is the receptor activity modifier protein 1, RCP is the receptor component protein, and ER is the endoplasmic reticulum.
Figure 2. CGRP cellular pathway. CGRP transmits signals to the cell using the G protein-coupled receptor-CLR-RAMP1 dimer: 1. cAMP signaling pathway: activates the G protein and AC to increase the intracellular second messenger. cAMP concentration activates PKA and CREB and promotes mRNA transcription in the nucleus. 2. Phosphatidylinositol signaling pathway: by activating PLCβ1, hydrolyzing PIP2 to generate second messengers, IP3 and DAG. IP3 is gated with the IP3 ligand on the endoplasmic reticulum. Calcium channel binding elevates the intracellular Ca2+ concentration and activates various calcium ion-dependent proteins. DAG rivets on the cell membrane to activate PKC bound to the cell membrane. Moreover, intracellular free PKC can phosphorylate the serine/threonine residues of proteins and have a biological effect. AC is adenylate cyclase. cAMP is cyclic adenosine monophosphate, PKA is protein kinase A, CREB is cyclic adenosine monophosphate response element binding protein, PLCβ1 is the phospholipase C, β1, IP3 is inositol 1,4,5-triphosphate, DAG is the diacylglycerol, PIP2 is the phosphatidylinositol-4,5-bisphosphate, PKC is a protein kinase C, CGRP is a calcitonin gene-related peptide, CLR is a calcitonin gene-related Peptide receptor, RAMP1 is the receptor activity modifier protein 1, RCP is the receptor component protein, and ER is the endoplasmic reticulum.
Biomolecules 13 00838 g002
Table
Table 1. CGRP antagonists.
Table 1. CGRP antagonists.
Target SpotNameTypeCurrent Status
CGRPROlcegepant [35]NonpeptidePhase II Clinical Trial
CGRPRTelcegepant [36]NonpeptidePhase III Clinical Trial
CGRPRMK-3207 [37]NonpeptidePhase II Clinical Trial
CGRPRZavegapant [38]NonpeptidePhase II/III Clinical Trial
CGRPRBI 44,370 [39]NonpeptidePhase II Clinical Trial
CGRPRErenumab [40]Monoclonal antibodyFDA approved in 2018
CGRPRRimegepant [41]NonpeptideFDA approved in 2020
CGRPRUbrogepant [42]NonpeptideFDA approved in 2020
CGRPRAtogepant [43]NonpeptideFDA approved in 2022
CGRPGalcanezumab [44]Monoclonal antibodyFDA approved in 2018
CGRPFremanezumab [45]Monoclonal antibodyFDA approved in 2018
CGRPEptinezumab [46]Monoclonal antibodyFDA approved in 2020
Table
Table 2. Study on CGRP at the cellular level.
Table 2. Study on CGRP at the cellular level.
Cell CategoryAuthorYearSignal PathwayExperimental Results
BMSCsLiping Wang [72]2010RANKL/NF-κBEnhance the osteogenic differentiation ability and inhibit osteoclast formation
Wei Liang [63]2015 ALP, collagen I, BMP2, osteonectin, and RUNX2 are upregulated, leading to increased proliferation and osteogenic differentiation
Ri Zhou [74]2016Wnt/β-cateninEnhance the osteogenic differentiation ability
Jie Chen [105]2017 The proliferation and osteogenic differentiation abilities are enhanced, and the adipogenic differentiation is inhibited in a dose-dependent manner
Sen Jia [73]2019 The expression of ALP and RUNX2 is upregulated, and the proliferation and migration abilities are enhanced
Qin Zhang [106]2019Hippo/YapUpregulate ALP, RUNX2, and OPN
Yanjun Guo [93]2020 Enhanced expression of VEGF, ALP, and OPN and reduced production of reactive oxygen species (ROS) induced by high glucose
Hang Li [54]2021 The osteogenic differentiation ability is enhanced, and the adipogenic differentiation ability is weakened
OsteoblastMichelangeli [107]1989cAMPUpregulate cAMP
Vignery [62]1996cAMPInsulin-like growth factor expression is upregulated, and the osteogenic differentiation ability is elevated
Millet [99]1997cAMPInhibit the TNF-α production stimulated by lipopolysaccharide and IL-1, but promote IL6 expression
Villa [108]2000cAMP Enhance the proliferation ability
Mrak [109]2010Wnt/β-cateninInhibit apoptosis
Yang Bo [91]2013 The expression of OC, ALP, and collagen is upregulated, and the osteogenic ability differentiation is increased
Haitao He [64]2016RANKL/NF-κBATF4 and OC expression is upregulated, and the osteogenic differentiation ability is enhanced
MacrophageOwan [110]1994cAMPInhibit osteoclast formation
Feng [98]1997cAMPInhibit LPS-induced TNF-α upregulation
Yeong-Min [111]2014RANKL/NF-κBUpregulate OPG expression and inhibit bone resorption
Qin Zhang [103]2021Hippo/YapInhibit and promote the osteogenic factor secretion in M2 macrophages in the early and late stages, respectively
OsteoclastAkopian [80]2000cAMPInhibit osteoclast formation in a dose-dependent manner
Ishizuka [79]2005RANKL/NF-κBInhibit osteoclast formation
EPCsHaegerstrand [50]1990cAMPEnhance the proliferation ability
Shuai Zheng [87]2010cAMPActivate AMPK-eNOS and enhance angiogenesis
Yang Bo [91]2013 Upregulate OC, ALP, and COL expression in vascular endothelial cells and osteoblast co-culture system
Jianqun Wu [90]2018MAPKEnhance the proliferation ability and inhibit apoptosis
Jie Mi [86]2021PI3K/AKTThe proliferation ability and angiogenesis are enhanced. The osteogenic differentiation ability of BMSCs is increased
Ye Li [94]2021FAK/VEGFEnhanced migration ability, promote FAK phosphorylation of and upregulate VEGF expression
PDSCsYifeng Zhang [75]2016cAMPSP7 and ALP expression is upregulated, and proliferation and osteogenic differentiation ability are enhanced
DPSCsCalland [112]1997cAMPBMP2 expression is upregulated, and the osteogenic differentiation ability is elevated
MG63Gang Tian [71]2013cAMPBMP2 expression is upregulated, and the osteogenic differentiation ability is enhanced
ADSCsZhong Fang [113]2013 ALP expression in the overexpressed CGRP group is upregulated, and the cell proliferation and osteogenic differentiation ability are enhanced
DRGJie Mi [15]2021cAMPElectrical stimulation promotes the synthesis and release of CGRP in DRG and enhances the H-type blood vessel formation and osteoporotic fracture healing
Table
Table 3. Study on CGRP at the animal level.
Table 3. Study on CGRP at the animal level.
ModelAuthorYearModeling MethodPhenotype
Gene editingBallica [58]1999Construction of mouse model of CGRP overexpressionInhibit osteoclasts, stimulate insulin-like growth factor, and inhibit the tumor necrosis factor-α production
Hoff [122]2002Construction of CGRP knockout mouse modelThe bone mass of gene-knockout mice was maintained after ovariectomy, and that of gene-knockout wild-type mice decreased within two months.
Schinke [59]2004Construction of CALCA and CGRP knockout mouse modelCALCA knockout mice revealed a high bone mass, while CGRP knockout mice showed a low bone mass.
Toda [81]2008Construction of CGRP knockout mouse modelThe expression of vascular endothelial growth factor within wound granulation tissue of CGRP knockout mice decreased. Angiogenesis and wound closure was significantly inhibited.
Lei Yang [97]2013Construction of CGRP knockout mouse modelCGRP can inhibit oxidative stress and the proliferation of vascular smooth muscle cells induced by vascular injury.
Kauther [123]2013Construction of CGRP knockout mouse modelIn mice, OPG and OCN increased significantly, osteoclasts elevated, and RANKL decreased significantly.
Takahashi [78]2016Construction of TRPV1 knockout mouse modelTRPV1 affects osteoclast formation by CGRP regulation
Niedermair [100]2020Construction of CGRP knockout mouse modelCGRP relieved pain and promoted the polarization of M2 macrophages but did not affect bone maturation.
Appelt [76]2020Construction of CGRP knockout mouse modelThe number of bone-forming osteoblasts in CGRP-deficient mice decreased significantly, and bone healing was poor.
Bone graftZhong Fang [113]2013Implantation of CGRP overexpressed ADSCs/β-TCP BracketADSCs overexpressing the CGRP/β-TCP stent promotes bone repair
Wei Liang [124]2016Implantation of CPC containing CGRP and SrCPC containing CGRP and Sr promotes bone repair among osteoporotic rats
Xijiao Yu [125]2019Implantation of CGRP overexpressed collagen scaffolds in BMSCsBMScs collagen scaffold overexpressing CGRP leads to skull repair in rats
Sen Jia [73]2019Construction of a rat model of distraction osteogenesisCGRP enhances new bone formation by elevating the migration and differentiation of bone marrow stromal cells.
Ye Li [94]2021Construction of a rat model of distraction osteogenesisMagnesium-containing intramedullary nail promotes bone defect repair in rats by the upregulating CGRP/FAK/VEGF pathway.
Wangyong Zhu [92]2021Construction of a rat model of drug-related osteonecrosisMagnesium grafts promote angiogenesis and bone repair by regulating VEGF and CGRP, thereby alleviating drug-related osteonecrosis.
Injection of drugsMapp [88]2012Normal knee jointPromote angiogenesis
Yanjun Guo [93]2020Construction of diabetic rat modelCGRP injection overexpressed BMSCs can elevate ALP activity and promote mRNA and protein expression of VEGF, ALP, and OPN
Hang Li2021Construction of senile mouse model and osteoporotic mouse modelPromote bone formation in aged mice, decrease fat accumulation, and delay osteoporosis occurrence in mice.
OtherAoki [82]1994Tibial bone defect modelLocal blood flow and callus formation increased.
Irie [126]2002Normal bone tissueThere are abundant CGRP-positive nerve fibers around the bone tissue.
Maeda [84]2017Normal fetal rat bone tissueCGRP is essential in osteogenesis and angiogenesis in bone development.
Feng Gao [127]2018Construction of obese mouse modelIn obese mice, CGRP, FGF, and TGF-β levels decreased, while TNF-α levels increased, and bone repair was delayed.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Wang, Q.; Qin, H.; Deng, J.; Xu, H.; Liu, S.; Weng, J.; Zeng, H. Research Progress in Calcitonin Gene-Related Peptide and Bone Repair. Biomolecules 2023, 13, 838. https://doi.org/10.3390/biom13050838

AMA Style

Wang Q, Qin H, Deng J, Xu H, Liu S, Weng J, Zeng H. Research Progress in Calcitonin Gene-Related Peptide and Bone Repair. Biomolecules. 2023; 13(5):838. https://doi.org/10.3390/biom13050838

Chicago/Turabian Style

Wang, Qichang, Haotian Qin, Jiapeng Deng, Huihui Xu, Su Liu, Jian Weng, and Hui Zeng. 2023. "Research Progress in Calcitonin Gene-Related Peptide and Bone Repair" Biomolecules 13, no. 5: 838. https://doi.org/10.3390/biom13050838

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop